Solar Energy
Solar Energy – Status and Perspectives Peter Ahm, Director PA Energy A/S (Ltd.) Snovdrupvej 16, DK-8340 Malling Phone: +45 86 93 33 33; Fax: +45 86 93 36 05; e-mail: [email protected]
Abstract Solar energy in terms of thermal Solar Hot Water systems and electricity producing Photovoltaics contribute at present only to the global energy supply at a fraction of 1 %. However, the potential for solar energy is immense: the earth receives in 1 hour from the sun the equivalent of the present annual global energy supply. Solar energy is one of the emerging renewable energy technologies still not competitive, but exhibiting both technical and economic potential to be so inside 10-15 years. There is basically no necessary “technology jumps” as prerequisites, but such a development will demand a favorable political climate. Growing political awareness, driven partly by environmental concerns partly by concerns about security of energy supply, of the need to promote solar energy and renewables, e.g. on global level spurred on by the recent UN/IPCC report and on an EU level by the EC commitment to reach 20 % renewables in the electricity supply by 2010 and 20 % renewables in the overall energy production by 2020, appears to ensure the necessary future political support for renewables, but not necessarily for solar energy technologies, in particular photovoltaics’s, which is still not yet competitive to other renewables although exhibiting a tremendous potential.
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1 Introduction The potential for solar energy is very high – about one hour sunshine on the surface of the earth corresponds to the present annual global energy consumption. However renewable and solar energy still plays a very minor role in the global energy supply. The IEA statistics1 as shown in Fig. 1 illustrates this fact very well.
Fig. 1: Fuel shares in 2004.
Although the contribution of solar energy to the global energy supply is quite small at present, less than 0,05 percent, the growth rate of solar energy has been relatively high, albeit from a very low starting point. Again with reference to IEA statistics and as
Fig. 2: Annual growth rates of renewables
illustrated in Fig. 2 renewables as such have in the period 1971 to 2004 exhibited an annual growth rate of 2,3 percent, almost on par with the growth rate of the global energy supply, whereas solar energy in the same period grew by almost 30 % per year in average with higher growth rates in the recent years.
1
Source: Renewables in Global Energy Supply, September 2006, the International Energy Agency.
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Being an emerging market segment, solar energy as other renewables is still dependent on political support. Growing political awareness, driven partly by environmental concerns partly by concerns about security of energy supply, of the need to promote solar energy and renewables, e.g. on global level spurred on by the recent UN/IPCC report and on an EU level by the EC commitment to reach 20 % renewables in the electricity supply by 2010 and 20 % renewables in the overall energy production by 2020, appears to ensure the necessary future political support for renewables, but not necessarily for solar energy technologies, in particular photovoltaics’s, which is still not yet competitive to other renewables although exhibiting a tremendous potential. Status and perspectives for solar energy in terms of solar hot water systems (SHW) and photovoltaics (PV) will be discussed in the following chapters, which have been prepared based on recent work done in connection with the Sustainable Energy Catalogue compiled by the Danish Board of Technology.
2 Solar Hot Water Systems 2.1 Technology information Solar thermal technology converts part of the energy content of the insolation into heat. Sub-technologies include flat plate collector systems2 typically for domestic hot water and other low temperature applications such as space heating or large scale district heating, parabolic troughs/evacuated tube collectors for higher temperature applications such as industrial process heat, and central thermal power stations with heliostats3 concentrating the insolation from a large area on a small receiver, in this way obtaining high temperatures and capacities suitable for operating steam turbines. Typical solar thermal conversion efficiencies range from about 25-60%. The two first mentioned sub-technologies are fully commercial and in operation in many countries all over the world. A solar heating system transforms the energy of the sun to heat, typically in a single, closed circuit. The solar collector consists of a black plate, which picks up the energy of the sun and heats up a mixture of water and antifreeze, which is pumped to a special hotwater tank in the house, where it emits the heat and runs back to the solar collector. Solar collectors are typically used for heating up domestic water, but more and more people also use solar-heated water for floor heating and other space heating. The system is adapted to the size of the house and the heating requirements. Furthermore, a new and promising use of solar heating is being developed – solar cooling. By attaching a solar collector that can heat water to 80 to 100 degrees to an absorption cooler, it is possible to create refrigeration, which for example can be used in air-conditioning systems. As the world uses more energy on cooling than on heating, great energy-saving perspectives in the solar cooling area become available. By the end of 2004, about 110 million m2 of solar collectors were installed worldwide. The energy contribution from this technology can be calculated using the IEA adopted conversion factor of 1 m2 = 0.7 kWTH. As to technology, about 25 pct. is unglazed collectors, mainly serving swimming pools, and 75 pct. is flat-plate and evacuated-tube collectors, predominantly for preparing hot water and for space heating. The average market growth rate has been 17-20 pct. in recent years. The most dynamic market areas are China and Europe. By 2004, China shows about 65 million m2 installed capacity
2
Thermo siphon’s or with forced circulation
3
A Heliostat is a device that tracks the movement of the sun.
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corresponding to 50 m2/1000 inhabitants. The EU exhibits about 14 million m2 installed capacity with wide variation from country to country. The presently installed solar thermal capacity provides around 0.15 pct. of the overall EU requirements for hot water and space heating. Used predominantly for hot water and space heating, solar thermal collectors are typically mounted on roofs of buildings, and as solar thermal installations are quite visible, this has lead to an ongoing process of both technological and architectural development. The aesthetics of a building is one of the most important aspects when solar collectors are “integrated” into the building envelope, the main trend being to try to make the solar collectors as invisible as possible. However, architects have started to use solar thermal installations in order to enhance the aesthetic appeal of a given building, but much more research and development seems to be needed in this field. In general, system costs decrease with the size of the system. Therefore, solar thermal systems connected to a district heating network are more cost-effective than systems for single family houses. Traditionally, short term storage is included in a solar thermal system in the range of 50-75 liters per m2 collector. Seasonal storage in the range of 2000 liters per m2 collector area has been investigated, but is still very much a research and development issue. 2.2 Best available technology Today (2006), vacuum tube solar collectors are the best with regard to performance. The somewhat higher price of these systems, compared to other product types, is usually compensated for by the better performance. 2.3 Supply potential A solar collector that covers an area of 4-5 m2 can typically cover 60-65% of the annual energy consumption of hot water for a family of 3-4 people. During the summer months, a facility like this will even cover the hot water need 100%. An average system that is targeted at space heating as well as hot domestic water can typically cover 30-40% of the annual heat consumption of a household depending on the geographical region. As mentioned, the EU has an objective4 that there should be 0.25 m2 solar collector per citizen in the member countries in 2010, which corresponds to a total of approx. 100 million m2. However, with the present market trends, only about 40-50 million m2 is likely to be reached by 2010. In 2005, Germany installed about 950.000 m2 totalling 4.700 million m2 (3.300 MWTH). About 4 % of German homes use SHW in 2005. Also in 2005, Austria installed about 240.000 m2, Spain almost 1 million m2 and France about 120.000 m2. 2.4 Environmental impact A solar heating system does not emit any CO2 or any other harmful substances to the atmosphere. An amount of power that corresponds to a light bulb is used for the system’s control function and pump. Most solar heating manufacturers take worn-out systems back and reuse some of the parts. The radiator coolant used is non-toxic. The energy used to produce a solar heating system corresponds to the energy that is produced by the system during approx. 9 months of operation. 2.5 Technology lifetime An average solar heating system with a life span of at least 20 years, which is installed by a workman in a home with electrical heating, will have paid for itself through saved energy costs within 7-8 years. If the system is installed in a home with oil/gas heating, the investment will have paid for itself within 12-15 years in Northern Europe. The annual operating costs of a solar heating system make up approx. 1% of the system price.
4
EU White Paper on Renewable Energies, COM(97)599, 26.11.97; EU Directive 2001/77/EC.
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Operating costs consist primarily of the power consumption of the pump that keeps the system running. 2.6 Economy A typical single family household SHW system of 4-5 m2 collector areas and 200-300 litres of storage tank ranges from 2-4000 €, but this depends considerably on the country and brand of manufacture. 2.7 Interaction with the energy system It appears from the EU’s White Paper containing, amongst others, solar heating5 that solar heating is assessed to have a good chance of becoming a profitable type of energy in connection with large, central heat and power stations. In 2004, the large solar heating systems that are attached to district heating stations are close to becoming a competitive alternative to gas and oil. It is advantageous to combine solar heating systems with biofuel systems (such as wood pellet burners), which can supply heat during the winter, when the solar heating system is less active. At the same time, it is an advantage to be able to turn off the boiler – typically during the summer. A biofuel boiler burns poorly at low load operation, which results in low efficiency and thus poor heating economy. When fuelling with biofuels, it is possible to use a highly efficient boiler with an attached storage tank, where the heated water is stored for use during the day and night. It is a good idea for the supply of hot water to the storage tank to come from a boiler as well as a solar heating system, as it reduces the need for continuous stoking in the boiler. Whether this method is financially attractive depends on the price of firewood. 2.8 Geographical parameters Leaders in the EU are Cyprus with 680 m2/1000 inhabitants followed by Greece and Austria with some 260 m2/1000 inhabitants, to Denmark with about 60 m2/1000 inhabitants. Israel probably has the highest penetration of solar thermals with about 740 m2/1000 inhabitants. In absolute terms, the European solar thermal market is dominated by Germany (50 %) followed by Greece and Austria (each 12 %). On a global level and in absolute numbers China leads with about 10 mill. m2 collector areas installed per year. 2.9 Advantages • A solar heating system does not emit any CO2 or other harmful substances to the atmosphere. • When a solar heating system has been paid through savings on the heating bill, the sun supplies free heat year after year. • A frequent criticism is that solar collectors disfigure buildings with their unattractive appearance. However, today, systems have been developed that are integrated into the roof surface in a harmonious way. 2.10 Disadvantages • A solar heating system in Europe can typically not stand alone, but has to be supplemented by another type of energy, because the sun exhibits considerable seasonal variation. • Solar heating is presently in general more expensive than fossil energy. 2.11 Timeline • 2006: the technology is fully developed and ready. Continuous smaller efficiency improvements are expected. The technology is adequately covered in terms of norms and standards. • 2004-2010: intermediate period for solar heating. Scattered distribution of inexpensive systems. • 2005-2010: possibility of some distribution of cooling through solar heating of buildings.
5
EU White Paper on Renewable Energies, COM(97)599, 26.11.97; EU Directive 2001/77/EC.
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• • •
2010-: good possibility of growing distribution to houses and buildings, in particular due to the EU Directive on Energy Consumption in Buildings. Presupposes subsidy scheme or rising oil and gas prices. 2015: 100 million m2 installed6. ESTIF has primo 2007 published a Solar Thermal Action Plan for Europe looking up to 2020 with a potential target of 1 m2 collector area/inhabitant, corresponding to about 320 GWTH.
3 Photovoltaic Systems 3.1 Technology information Photovoltaic (PV) power systems convert light directly into electricity without any moving parts or any emissions, which means PV systems can normally – unless very little physical space is available – be implemented directly at the site of the electric load to be supplied, one of the great advantages of PV technology (on-site generation). R&D of PV technology has since the early 1970’s been supported both on the EU level and by the EU member states, and the EU constitutes presently a centre of excellence in the field of PV technology. Although not yet competitive with other sources of electricity, PV is widely regarded as a significant contributor to the future electricity supply of Europe, and to stimulate this evolution, a PV Technology Platform was established in 2005 encompassing all important EU stakeholders. Typical conversion efficiency for a Silicon PV module is 14-16 %, the best commercial modules exhibiting 20-21 % efficiency. PV modules and systems are much better documented and tested than most other industrial products. The reason for this is that the technology was originally developed for space travel and military purposes, where it had to meet very strict requirements. Today, the main market is PV systems connected to the electric grid, but there is also a considerable market for stand-alone systems, in particular for remote professional applications such as signalling and telecom, water pumping, cathodic protection and similar. In developing countries, small stand-alone systems (Solar Home Systems) are used for household electrification outside the grid coverage. The global market for traditional photovoltaics (PV) has in the last 5 years seen an annual rate of growth of about 40%. In 2004, the growth was more than 60%, and in 2005 about 43%; the estimate for 2006 is 40 %. Even if the base in terms of energy production is quite small, the global PV market in 2005 exhibited a value of more than 10 billion €. The market is mainly traditional Silicon-based crystalline cells and modules. In 2005, almost 90% of the PV modules produced were based on crystalline Silicon technology, with poly-crystalline Silicon modules constituting about 60%. Since 2004, lack of Silicon feed-stock has led to an increase in PV module cost and a slight increase in system cost and this has established a real “sellers market”. Since 2005, the Silicon industry has invested heavily in increased production capacity and this feed-stock bottleneck is expected to be cleared during 2007-8. Crystalline Silicon cells and modules are expected to dominate the market in the coming 10-15 years and only after about 20 years are they expected to cover less than 50 pct. of the global PV market. The EU has in 2005 launched a PV Technology Platform and regards PV as a significant future energy technology for the Union. The EU goal of reaching 3 GW installed PV capacity by 2010 (1% of the EU electricity consumption) is presently expected to be exceeded, as 4.5-5 GW installed capacity is regarded as realistic by 2010. 3.2 Best available technology
6
Estimated by ESTIF – European Solar Thermal Industry Federation (www.estif.org) – with support of active policies.
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A typical system for a one-family house that is self-sufficient with regard to electricity is of 15-35 m2, which corresponds to a power of 2-5 kW (depending on PV cell type). In northern Europe, a PV system can produce approx. 850-900 kWh/year for each kW of generating capacity; in southern Europe, almost the double. Recently, PV modules with efficiencies of more than 20% have been introduced onto the market – which means that the necessary solar cell area can be significantly reduced. On the installation side, there are now also so-called “plug-and-play” systems, which are plugged directly into the socket and thus displace purchased electricity. Traditional PV technology has a learning curve typically showing a learning rate of some 20% , signifying a reduction in cost of 20% every time the volume is doubled. This trend is expected to continue for the next 10-15 years, as a combination of reduced material (Silicon) consumption and improved production technology will make this possible without any demand for “new technology”. Thin film PV module types with strongly reduced manufacturing costs are slowly gaining ground and will probably take a prominent position in the future. However, they still exhibit lower efficiency and lower stability compared to crystalline PV modules. 3.3 Supply potential A number of scenarios7 have been developed for future PV penetration in the EU and in the individual member countries. Maximum penetration foreseen up to 2040 ranges from between 20-40% of all electricity consumed, corresponding to 60-120 GW installed capacity. However, these forecasts are inherently very uncertain and depend very much on energy policies, raw material supplies, manufacturing capacities and in particular price developments. It is relatively easy to forecast the production of electricity from PV systems and to integrate the electricity into a given electricity grid system. The main area of application in Europe appears to be building integrated PV systems (BIPV), where the PV technology can be applied in urban areas, not taking up new space, can easily be connected to the grid, is close to the actual consumption of electricity and can fulfil “multi-functions” in a building, e.g. be an integral part of the building envelope as well as produce electricity. 3.4 Environmental impact PV modules do not have any impact on the environment during operation. The total cradle-to-grave environmental impact of typical PV Silicon modules is very limited. Recycling of PV modules and the associated electronics is well-known and the possibilities are continuously being improved. Health and environmental issues related to PV technology are being studied and investigated internationally, e.g. in the framework of the International Energy Agency (IEA). The consumption of energy for manufacturing a PV module will usually be produced by the module within approx. 3-4 years. The economic lifetime is typically 30 years or more. This means that the solar cells produce almost ten times as much energy as the amount of energy used for manufacturing and operating the solar cell system. If solar cells replace other building materials, the energy balance can become even better. 3.5 Technology lifetime The economic lifetime of present typical state-of-the art PV systems in Europe is 30 years. However, the PV modules themselves can be expected to last longer. On the other hand, PV technology develops quite quickly, and old installations may be considered obsolete earlier due to this technical progress.
7
For example: EPIA & Greenpeace: Solar Generation; The EU PV Technology Research Advisory Council: A Vision for PV Technology; Photon International Magazine.
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3.6 Economy The cost of electricity from PV systems has to be reduced significantly to become a real alternative to electricity supply based on fossil fuels and thereby achieve a break-through in the energy sector. Since the beginning of the 1980s, the price of solar cell modules has been halved every 7 years. In Europe, the present cost of electricity from PV systems is around 0.3-0.4 €/kWh in northern Europe and half of that for the best systems in southern Europe. These costs can be reduced by increasing the efficiency of PV systems or by reducing the overall costs – both happen continuously through research and development in materials, processes, design, etc. At the same time, growing production volumes also lead to falling prices. The global PV industry exhibits a very nontransparent relationship between prices and cost. At present, PV systems are reported to be competitive as peak-load shaver in southern Europe. In general terms, PV systems are expected to be competitive in Europe inside 812 years. 3.7 Interaction with the energy system There seems to be little in terms of technical constraints even for a large-scale penetration of PV technology into a given grid system. There is normally good correlation between PV production and the need of electricity and PV production is relatively easy to forecast accurately. Many investigations have shown that modern inverter technology does not impair power quality – on the contrary. 3.8 Geographical parameters Europe exhibits considerable differences in insolation – in yearly average, a factor 1:2 from northern to southern Europe and, more importantly, a seasonal variation in the north of 1:10 compared to 1:4 in the south. Besides the resource variations, the value of PV produced electricity differs considerably across Europe, depending on factors such as load profiles, type and operation of generators, feed-in tariff structures and cost of fuel. 3.9 Advantages • PV systems do not have any environmental impact during operation. • PV systems constitute a robust and reliable type of energy production with few operating costs and a long lifespan. • Power is produced during the day, when the demand is largest. • PV systems are scale neutral in efficiency – small systems are as energy efficient as large systems • A PV system consists of individual solar modules and can be expanded to MW or GW in system size – like building blocks, more solar modules can be put together to create a system theoretically with no limit in size8. • PV systems are easy to adapt to the electrical power network, as decentralised as well as central production. • There are good possibilities for integrating PV systems into the urban environment and into buildings. 3.10 Disadvantages • The price of a PV system is still relatively high, and the technology is not yet competitive with the alternatives supplying the electrical grid systems. However, prices are expected to fall continuously for quite a considerable time in the future and to reach competitiveness in about 10 years.
8
Very Large Scale Photovoltaic Power Generations Systems (VLS-PV) are examined by IEA-PVPS http://www.iea-pvps.org/tasks/task8.htm
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Timeline • 2005-2010: solar cells are more and more being architecturally integrated into buildings (BIPV), a trend also expected to be stimulated by the EU energy & building directive. • 2010: Standard Silicon based PV module cost a < 1,5 €/W; increased area of competitiveness for PV electricity • 2010: commercial break-through for third generation solar cells. This will result in integration of inexpensive solar cells in windows and many other building and consumer goods. • 2015: standard Silicon PV module cost < 1€/W. PV systems play an important role in connection with solving peak load problems of the electrical power network. • 2015-2020: solar cells are expected to be directly competitive to alternative electricity producing technologies. • The EPIA & Greenpeace scenario (see footnote 7) shows, that by 2025 PV on global level may produce about 590 TWh corresponding to an installed capacity of about 430 GW. The EU25 would have 20 % of its electricity coming from PV. 2025: emergence of solar cells that have an integrated electrolysis function and can therefore produce hydrogen for use as a propellant in fuel cells.
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Abstract Solar energy in terms of thermal Solar Hot Water systems and electricity producing Photovoltaics contribute at present only to the global energy supply at a fraction of 1 %. However, the potential for solar energy is immense: the earth receives in 1 hour from the sun the equivalent of the present annual global energy supply. Solar energy is one of the emerging renewable energy technologies still not competitive, but exhibiting both technical and economic potential to be so inside 10-15 years. There is basically no necessary “technology jumps” as prerequisites, but such a development will demand a favorable political climate. Growing political awareness, driven partly by environmental concerns partly by concerns about security of energy supply, of the need to promote solar energy and renewables, e.g. on global level spurred on by the recent UN/IPCC report and on an EU level by the EC commitment to reach 20 % renewables in the electricity supply by 2010 and 20 % renewables in the overall energy production by 2020, appears to ensure the necessary future political support for renewables, but not necessarily for solar energy technologies, in particular photovoltaics’s, which is still not yet competitive to other renewables although exhibiting a tremendous potential.
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1 Introduction The potential for solar energy is very high – about one hour sunshine on the surface of the earth corresponds to the present annual global energy consumption. However renewable and solar energy still plays a very minor role in the global energy supply. The IEA statistics1 as shown in Fig. 1 illustrates this fact very well.
Fig. 1: Fuel shares in 2004.
Although the contribution of solar energy to the global energy supply is quite small at present, less than 0,05 percent, the growth rate of solar energy has been relatively high, albeit from a very low starting point. Again with reference to IEA statistics and as
Fig. 2: Annual growth rates of renewables
illustrated in Fig. 2 renewables as such have in the period 1971 to 2004 exhibited an annual growth rate of 2,3 percent, almost on par with the growth rate of the global energy supply, whereas solar energy in the same period grew by almost 30 % per year in average with higher growth rates in the recent years.
1
Source: Renewables in Global Energy Supply, September 2006, the International Energy Agency.
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Being an emerging market segment, solar energy as other renewables is still dependent on political support. Growing political awareness, driven partly by environmental concerns partly by concerns about security of energy supply, of the need to promote solar energy and renewables, e.g. on global level spurred on by the recent UN/IPCC report and on an EU level by the EC commitment to reach 20 % renewables in the electricity supply by 2010 and 20 % renewables in the overall energy production by 2020, appears to ensure the necessary future political support for renewables, but not necessarily for solar energy technologies, in particular photovoltaics’s, which is still not yet competitive to other renewables although exhibiting a tremendous potential. Status and perspectives for solar energy in terms of solar hot water systems (SHW) and photovoltaics (PV) will be discussed in the following chapters, which have been prepared based on recent work done in connection with the Sustainable Energy Catalogue compiled by the Danish Board of Technology.
2 Solar Hot Water Systems 2.1 Technology information Solar thermal technology converts part of the energy content of the insolation into heat. Sub-technologies include flat plate collector systems2 typically for domestic hot water and other low temperature applications such as space heating or large scale district heating, parabolic troughs/evacuated tube collectors for higher temperature applications such as industrial process heat, and central thermal power stations with heliostats3 concentrating the insolation from a large area on a small receiver, in this way obtaining high temperatures and capacities suitable for operating steam turbines. Typical solar thermal conversion efficiencies range from about 25-60%. The two first mentioned sub-technologies are fully commercial and in operation in many countries all over the world. A solar heating system transforms the energy of the sun to heat, typically in a single, closed circuit. The solar collector consists of a black plate, which picks up the energy of the sun and heats up a mixture of water and antifreeze, which is pumped to a special hotwater tank in the house, where it emits the heat and runs back to the solar collector. Solar collectors are typically used for heating up domestic water, but more and more people also use solar-heated water for floor heating and other space heating. The system is adapted to the size of the house and the heating requirements. Furthermore, a new and promising use of solar heating is being developed – solar cooling. By attaching a solar collector that can heat water to 80 to 100 degrees to an absorption cooler, it is possible to create refrigeration, which for example can be used in air-conditioning systems. As the world uses more energy on cooling than on heating, great energy-saving perspectives in the solar cooling area become available. By the end of 2004, about 110 million m2 of solar collectors were installed worldwide. The energy contribution from this technology can be calculated using the IEA adopted conversion factor of 1 m2 = 0.7 kWTH. As to technology, about 25 pct. is unglazed collectors, mainly serving swimming pools, and 75 pct. is flat-plate and evacuated-tube collectors, predominantly for preparing hot water and for space heating. The average market growth rate has been 17-20 pct. in recent years. The most dynamic market areas are China and Europe. By 2004, China shows about 65 million m2 installed capacity
2
Thermo siphon’s or with forced circulation
3
A Heliostat is a device that tracks the movement of the sun.
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corresponding to 50 m2/1000 inhabitants. The EU exhibits about 14 million m2 installed capacity with wide variation from country to country. The presently installed solar thermal capacity provides around 0.15 pct. of the overall EU requirements for hot water and space heating. Used predominantly for hot water and space heating, solar thermal collectors are typically mounted on roofs of buildings, and as solar thermal installations are quite visible, this has lead to an ongoing process of both technological and architectural development. The aesthetics of a building is one of the most important aspects when solar collectors are “integrated” into the building envelope, the main trend being to try to make the solar collectors as invisible as possible. However, architects have started to use solar thermal installations in order to enhance the aesthetic appeal of a given building, but much more research and development seems to be needed in this field. In general, system costs decrease with the size of the system. Therefore, solar thermal systems connected to a district heating network are more cost-effective than systems for single family houses. Traditionally, short term storage is included in a solar thermal system in the range of 50-75 liters per m2 collector. Seasonal storage in the range of 2000 liters per m2 collector area has been investigated, but is still very much a research and development issue. 2.2 Best available technology Today (2006), vacuum tube solar collectors are the best with regard to performance. The somewhat higher price of these systems, compared to other product types, is usually compensated for by the better performance. 2.3 Supply potential A solar collector that covers an area of 4-5 m2 can typically cover 60-65% of the annual energy consumption of hot water for a family of 3-4 people. During the summer months, a facility like this will even cover the hot water need 100%. An average system that is targeted at space heating as well as hot domestic water can typically cover 30-40% of the annual heat consumption of a household depending on the geographical region. As mentioned, the EU has an objective4 that there should be 0.25 m2 solar collector per citizen in the member countries in 2010, which corresponds to a total of approx. 100 million m2. However, with the present market trends, only about 40-50 million m2 is likely to be reached by 2010. In 2005, Germany installed about 950.000 m2 totalling 4.700 million m2 (3.300 MWTH). About 4 % of German homes use SHW in 2005. Also in 2005, Austria installed about 240.000 m2, Spain almost 1 million m2 and France about 120.000 m2. 2.4 Environmental impact A solar heating system does not emit any CO2 or any other harmful substances to the atmosphere. An amount of power that corresponds to a light bulb is used for the system’s control function and pump. Most solar heating manufacturers take worn-out systems back and reuse some of the parts. The radiator coolant used is non-toxic. The energy used to produce a solar heating system corresponds to the energy that is produced by the system during approx. 9 months of operation. 2.5 Technology lifetime An average solar heating system with a life span of at least 20 years, which is installed by a workman in a home with electrical heating, will have paid for itself through saved energy costs within 7-8 years. If the system is installed in a home with oil/gas heating, the investment will have paid for itself within 12-15 years in Northern Europe. The annual operating costs of a solar heating system make up approx. 1% of the system price.
4
EU White Paper on Renewable Energies, COM(97)599, 26.11.97; EU Directive 2001/77/EC.
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Operating costs consist primarily of the power consumption of the pump that keeps the system running. 2.6 Economy A typical single family household SHW system of 4-5 m2 collector areas and 200-300 litres of storage tank ranges from 2-4000 €, but this depends considerably on the country and brand of manufacture. 2.7 Interaction with the energy system It appears from the EU’s White Paper containing, amongst others, solar heating5 that solar heating is assessed to have a good chance of becoming a profitable type of energy in connection with large, central heat and power stations. In 2004, the large solar heating systems that are attached to district heating stations are close to becoming a competitive alternative to gas and oil. It is advantageous to combine solar heating systems with biofuel systems (such as wood pellet burners), which can supply heat during the winter, when the solar heating system is less active. At the same time, it is an advantage to be able to turn off the boiler – typically during the summer. A biofuel boiler burns poorly at low load operation, which results in low efficiency and thus poor heating economy. When fuelling with biofuels, it is possible to use a highly efficient boiler with an attached storage tank, where the heated water is stored for use during the day and night. It is a good idea for the supply of hot water to the storage tank to come from a boiler as well as a solar heating system, as it reduces the need for continuous stoking in the boiler. Whether this method is financially attractive depends on the price of firewood. 2.8 Geographical parameters Leaders in the EU are Cyprus with 680 m2/1000 inhabitants followed by Greece and Austria with some 260 m2/1000 inhabitants, to Denmark with about 60 m2/1000 inhabitants. Israel probably has the highest penetration of solar thermals with about 740 m2/1000 inhabitants. In absolute terms, the European solar thermal market is dominated by Germany (50 %) followed by Greece and Austria (each 12 %). On a global level and in absolute numbers China leads with about 10 mill. m2 collector areas installed per year. 2.9 Advantages • A solar heating system does not emit any CO2 or other harmful substances to the atmosphere. • When a solar heating system has been paid through savings on the heating bill, the sun supplies free heat year after year. • A frequent criticism is that solar collectors disfigure buildings with their unattractive appearance. However, today, systems have been developed that are integrated into the roof surface in a harmonious way. 2.10 Disadvantages • A solar heating system in Europe can typically not stand alone, but has to be supplemented by another type of energy, because the sun exhibits considerable seasonal variation. • Solar heating is presently in general more expensive than fossil energy. 2.11 Timeline • 2006: the technology is fully developed and ready. Continuous smaller efficiency improvements are expected. The technology is adequately covered in terms of norms and standards. • 2004-2010: intermediate period for solar heating. Scattered distribution of inexpensive systems. • 2005-2010: possibility of some distribution of cooling through solar heating of buildings.
5
EU White Paper on Renewable Energies, COM(97)599, 26.11.97; EU Directive 2001/77/EC.
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• • •
2010-: good possibility of growing distribution to houses and buildings, in particular due to the EU Directive on Energy Consumption in Buildings. Presupposes subsidy scheme or rising oil and gas prices. 2015: 100 million m2 installed6. ESTIF has primo 2007 published a Solar Thermal Action Plan for Europe looking up to 2020 with a potential target of 1 m2 collector area/inhabitant, corresponding to about 320 GWTH.
3 Photovoltaic Systems 3.1 Technology information Photovoltaic (PV) power systems convert light directly into electricity without any moving parts or any emissions, which means PV systems can normally – unless very little physical space is available – be implemented directly at the site of the electric load to be supplied, one of the great advantages of PV technology (on-site generation). R&D of PV technology has since the early 1970’s been supported both on the EU level and by the EU member states, and the EU constitutes presently a centre of excellence in the field of PV technology. Although not yet competitive with other sources of electricity, PV is widely regarded as a significant contributor to the future electricity supply of Europe, and to stimulate this evolution, a PV Technology Platform was established in 2005 encompassing all important EU stakeholders. Typical conversion efficiency for a Silicon PV module is 14-16 %, the best commercial modules exhibiting 20-21 % efficiency. PV modules and systems are much better documented and tested than most other industrial products. The reason for this is that the technology was originally developed for space travel and military purposes, where it had to meet very strict requirements. Today, the main market is PV systems connected to the electric grid, but there is also a considerable market for stand-alone systems, in particular for remote professional applications such as signalling and telecom, water pumping, cathodic protection and similar. In developing countries, small stand-alone systems (Solar Home Systems) are used for household electrification outside the grid coverage. The global market for traditional photovoltaics (PV) has in the last 5 years seen an annual rate of growth of about 40%. In 2004, the growth was more than 60%, and in 2005 about 43%; the estimate for 2006 is 40 %. Even if the base in terms of energy production is quite small, the global PV market in 2005 exhibited a value of more than 10 billion €. The market is mainly traditional Silicon-based crystalline cells and modules. In 2005, almost 90% of the PV modules produced were based on crystalline Silicon technology, with poly-crystalline Silicon modules constituting about 60%. Since 2004, lack of Silicon feed-stock has led to an increase in PV module cost and a slight increase in system cost and this has established a real “sellers market”. Since 2005, the Silicon industry has invested heavily in increased production capacity and this feed-stock bottleneck is expected to be cleared during 2007-8. Crystalline Silicon cells and modules are expected to dominate the market in the coming 10-15 years and only after about 20 years are they expected to cover less than 50 pct. of the global PV market. The EU has in 2005 launched a PV Technology Platform and regards PV as a significant future energy technology for the Union. The EU goal of reaching 3 GW installed PV capacity by 2010 (1% of the EU electricity consumption) is presently expected to be exceeded, as 4.5-5 GW installed capacity is regarded as realistic by 2010. 3.2 Best available technology
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Estimated by ESTIF – European Solar Thermal Industry Federation (www.estif.org) – with support of active policies.
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A typical system for a one-family house that is self-sufficient with regard to electricity is of 15-35 m2, which corresponds to a power of 2-5 kW (depending on PV cell type). In northern Europe, a PV system can produce approx. 850-900 kWh/year for each kW of generating capacity; in southern Europe, almost the double. Recently, PV modules with efficiencies of more than 20% have been introduced onto the market – which means that the necessary solar cell area can be significantly reduced. On the installation side, there are now also so-called “plug-and-play” systems, which are plugged directly into the socket and thus displace purchased electricity. Traditional PV technology has a learning curve typically showing a learning rate of some 20% , signifying a reduction in cost of 20% every time the volume is doubled. This trend is expected to continue for the next 10-15 years, as a combination of reduced material (Silicon) consumption and improved production technology will make this possible without any demand for “new technology”. Thin film PV module types with strongly reduced manufacturing costs are slowly gaining ground and will probably take a prominent position in the future. However, they still exhibit lower efficiency and lower stability compared to crystalline PV modules. 3.3 Supply potential A number of scenarios7 have been developed for future PV penetration in the EU and in the individual member countries. Maximum penetration foreseen up to 2040 ranges from between 20-40% of all electricity consumed, corresponding to 60-120 GW installed capacity. However, these forecasts are inherently very uncertain and depend very much on energy policies, raw material supplies, manufacturing capacities and in particular price developments. It is relatively easy to forecast the production of electricity from PV systems and to integrate the electricity into a given electricity grid system. The main area of application in Europe appears to be building integrated PV systems (BIPV), where the PV technology can be applied in urban areas, not taking up new space, can easily be connected to the grid, is close to the actual consumption of electricity and can fulfil “multi-functions” in a building, e.g. be an integral part of the building envelope as well as produce electricity. 3.4 Environmental impact PV modules do not have any impact on the environment during operation. The total cradle-to-grave environmental impact of typical PV Silicon modules is very limited. Recycling of PV modules and the associated electronics is well-known and the possibilities are continuously being improved. Health and environmental issues related to PV technology are being studied and investigated internationally, e.g. in the framework of the International Energy Agency (IEA). The consumption of energy for manufacturing a PV module will usually be produced by the module within approx. 3-4 years. The economic lifetime is typically 30 years or more. This means that the solar cells produce almost ten times as much energy as the amount of energy used for manufacturing and operating the solar cell system. If solar cells replace other building materials, the energy balance can become even better. 3.5 Technology lifetime The economic lifetime of present typical state-of-the art PV systems in Europe is 30 years. However, the PV modules themselves can be expected to last longer. On the other hand, PV technology develops quite quickly, and old installations may be considered obsolete earlier due to this technical progress.
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For example: EPIA & Greenpeace: Solar Generation; The EU PV Technology Research Advisory Council: A Vision for PV Technology; Photon International Magazine.
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3.6 Economy The cost of electricity from PV systems has to be reduced significantly to become a real alternative to electricity supply based on fossil fuels and thereby achieve a break-through in the energy sector. Since the beginning of the 1980s, the price of solar cell modules has been halved every 7 years. In Europe, the present cost of electricity from PV systems is around 0.3-0.4 €/kWh in northern Europe and half of that for the best systems in southern Europe. These costs can be reduced by increasing the efficiency of PV systems or by reducing the overall costs – both happen continuously through research and development in materials, processes, design, etc. At the same time, growing production volumes also lead to falling prices. The global PV industry exhibits a very nontransparent relationship between prices and cost. At present, PV systems are reported to be competitive as peak-load shaver in southern Europe. In general terms, PV systems are expected to be competitive in Europe inside 812 years. 3.7 Interaction with the energy system There seems to be little in terms of technical constraints even for a large-scale penetration of PV technology into a given grid system. There is normally good correlation between PV production and the need of electricity and PV production is relatively easy to forecast accurately. Many investigations have shown that modern inverter technology does not impair power quality – on the contrary. 3.8 Geographical parameters Europe exhibits considerable differences in insolation – in yearly average, a factor 1:2 from northern to southern Europe and, more importantly, a seasonal variation in the north of 1:10 compared to 1:4 in the south. Besides the resource variations, the value of PV produced electricity differs considerably across Europe, depending on factors such as load profiles, type and operation of generators, feed-in tariff structures and cost of fuel. 3.9 Advantages • PV systems do not have any environmental impact during operation. • PV systems constitute a robust and reliable type of energy production with few operating costs and a long lifespan. • Power is produced during the day, when the demand is largest. • PV systems are scale neutral in efficiency – small systems are as energy efficient as large systems • A PV system consists of individual solar modules and can be expanded to MW or GW in system size – like building blocks, more solar modules can be put together to create a system theoretically with no limit in size8. • PV systems are easy to adapt to the electrical power network, as decentralised as well as central production. • There are good possibilities for integrating PV systems into the urban environment and into buildings. 3.10 Disadvantages • The price of a PV system is still relatively high, and the technology is not yet competitive with the alternatives supplying the electrical grid systems. However, prices are expected to fall continuously for quite a considerable time in the future and to reach competitiveness in about 10 years.
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Very Large Scale Photovoltaic Power Generations Systems (VLS-PV) are examined by IEA-PVPS http://www.iea-pvps.org/tasks/task8.htm
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Timeline • 2005-2010: solar cells are more and more being architecturally integrated into buildings (BIPV), a trend also expected to be stimulated by the EU energy & building directive. • 2010: Standard Silicon based PV module cost a < 1,5 €/W; increased area of competitiveness for PV electricity • 2010: commercial break-through for third generation solar cells. This will result in integration of inexpensive solar cells in windows and many other building and consumer goods. • 2015: standard Silicon PV module cost < 1€/W. PV systems play an important role in connection with solving peak load problems of the electrical power network. • 2015-2020: solar cells are expected to be directly competitive to alternative electricity producing technologies. • The EPIA & Greenpeace scenario (see footnote 7) shows, that by 2025 PV on global level may produce about 590 TWh corresponding to an installed capacity of about 430 GW. The EU25 would have 20 % of its electricity coming from PV. 2025: emergence of solar cells that have an integrated electrolysis function and can therefore produce hydrogen for use as a propellant in fuel cells.
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